1. Field of the Invention
The present invention relates generally to IBM compatible personal computer systems. More specifically, the present invention relates to a digital computer system having an IBM compatible personal computer for providing a bridge between a host computer and PCMCIA memory cards which allows for data transfer between the host computer and the memory cards.
2. Description of the Prior Art
The Personal Memory Card International Association (PCMCIA) memory card is a widely accepted storage medium for use with personal computers. The memory card's small size, large storage capacity and ruggedness have made the memory card the ideal storage device for storage of data in military and civilian systems.
The personal computer memory card was originally developed for use with palm top and lab top MS-DOS compatible computers. During the course of development of the personal computer memory card, several different types of memory cards which use varying technologies and architectures have evolved.
The personal computer memory card is made from two primary technologies: (1) the Static Random Access Memory (SRAM) and (2) the Flash Electronically Erasable Programmable Read Only Memory (EEPROM). Static Random Access Memory Cards have a memory mapped architecture, while Flash Electronically Erasable Programmable Read Only Memory Cards have memory mapped series I and II and Advanced Technology Attachment (ATA) architectures.
A computer system or drive transferring data to a memory mapped PC memory card needs specific card parameters such as timing parameters for the card, block size and card memory size for a successful data transfer.
Series I memory cards do not have built in attribute sections containing the required card parameters. These card parameters must be transferred to the memory card along with the data for later extraction by a computer system having custom software.
Series II PC memory cards include an attribute section which has a standardized Card Information Structure (CIS) describing the memory card's device parameters. In addition, Series II PC memory cards have an on board controller to control write and erase timing functions which eliminates these functions from the computer system transferring the data.
Unlike ATA PC memory cards, memory mapped PC memory cards do not have a file system. These memory mapped PC cards may include memory mapped data dumps, programs that are executed in place, files which use a commercial flash file system or files which use a custom flash file system. In addition, Microsoft's FFS2 flash file system and M-System's TrueFFS flash file system, which are the two largest commercially available flash file systems, are not compatible.
Presently, a number PC Memory Card drives are not capable of interfacing with all PC memory cards. In particular, computers which are not compatible with IBM personal computers (MS-DOS compatible) can only interface with a limited number of PC memory cards. Further, a number of PC I/O Cards include device drives required by the memory card for operation which can only be run from an IBM compatible personal computer.
For example, there are commercially available from Adtron Corporation of Chandler, Arizona PC Card drives which interface to a host computer via the Small Computer Systems interface (SCSI). These PC Card drives allow the host computer to read, write to, format and erase ATA Flash Disk cards. However, these PC Card drives do not allow for (1)erasing, writing or formatting of PCMCIA Flash Memory cards; and (2) communication with some PC I/O cards. These PC Card drives are also limited to reading from and writing to pre-formatted Static Random Access Memory cards. Accordingly, there is a need for a PC card drive which is compatible with MS-DOS computer systems as well as other computers which do not use MS-DOS as the operating system. In addition, the PC card drive should support all utilities including writing to the memory card, formatting the memory card, reading the memory card and erasing the memory card.